FR2609239A1 - METHOD AND DEVICE FOR SUPPLYING TOBACCO TO A CIGARETTE MAKING MACHINE - Google Patents

Abstract

PROCESS FOR SUPPLYING TOBACCO FOR A CIGARETTE MAKING MACHINE WHICH CONSISTS OF TRANSPORTING TOBACCO PARTICLES IN AN AIR CURRENT FROM A TOBACCO DELIVERY DEVICE TO A HOPPER SYSTEM, MEASURING THE TOBACCO IN THE HOPPER SYSTEM AND A PNEUMATICALLY TRANSPORTING THE TOBACCO IN AN AIR CURRENT TO AN AIR-PERMEABLE SUCTION TAPE, IN ORDER TO FORM, BY EXTRACTION OF THE AIR CURRENT, A LAYER OF TOBACCO TO BE DELIVERED TO THE MEANS OF FORMATION OF A TOBACCO STEM OF THE CIGARETTE MAKING MACHINE, CHARACTERIZED IN THAT ATMOSPHERIC AIR IS INDUCED INTO THE TOBACCO DELIVERY DEVICE AND IT IS SUCCESSIVELY USED TO TRAIN AND TRANSPORT THE TOBACCO PARTICLES FROM THE DELIVERY DEVICE TOWARDS THE HOPPER SYSTEM AND TO TRAIN AND TRANSPORT THE TOBACCO PARTICLES FROM THE HOPPER SYSTEM TO THE SUCTION BAND, THE TOBACCO PARTICLES BEING RELEASED FROM THE TRAIN BY THE AIR CURRENT TO AN INPUT OF THE HOPPER SYSTEM. HOPPER AND TOBACCO MEASUREMENT FROM THE HOPPER SYSTEM BEING AGAIN DRAWN IN AT LEAST PART OF THE SAME AIR CURRENT, THE HOPPER SYSTEM OPERATING AT A PRESSURE LOWER THAN THE ATMOSPHERIC PRESSURE IN THE AIRFLOW SEPARATED FROM THE PARTICLES TOBACCO DELIVERED BY THE DELIVERY DEVICE.

Description

The present invention relates to a method and a device for

  feeding tobacco particles from an unopened (i.e. unventilated) source of tobacco, which has been cut, to form a continuous tobacco filler on a air permeable suction tape on the move in a cigarette making machine. During the manufacture of cigarettes, tobacco is generally transported pneumatically to a cigarette making machine from a central "primary" device serving a certain number of cigarette making machines. This system generally includes a tobacco delivery device (part of the primary device) which includes a source of cut tobacco and means for * bringing tobacco particles into a tobacco-carrying air stream which brings the tobacco to a hopper system associated with the cigarette making machine. This delivery device is generally actuated under the effect of the vacuum. A central fan operating through a vacuum distribution system is generally the source of vacuum. A pneumatic valve-type locking system must be used on each cigarette making machine to isolate the pressure, below atmospheric pressure, prevailing in the delivery device, from ambient atmospheric pressure, prevailing in a hopper of a classic cigarette making machine. The tobacco is discharged into the hopper from this pneumatic locking valve and the tobacco dust which remains in the air can be separated from the latter in a central filter which is located in the vicinity of the

central fan.

  It is common practice in the tobacco supply of cigarette machines, intermittently, that each delivery period is of sufficient duration to fill an unloading device which, then, serves as a buffer capacity to maintain a determined quantity of tobacco in the hopper when the latter requires tobacco. However, it has been proposed to provide a continuous or almost continuous supply of tobacco to each hopper system and the present invention relates more particularly to such systems. A conventional hopper system generally comprises a tobacco storage area and pre-measuring, measuring and opening devices which act on the tobacco so as to produce a thin and wide stream of separate tobacco particles which are entrained by a stream of air and transported to the air permeable suction band. Two fans are generally used which are located in the cigarette making machine. One of the fans creates a vacuum applied to the suction strip and the second fan (which is sometimes called the compressor) increases the air flow transporting the tobacco to the suction strip. Excess tobacco, trimmed on a continuous layer of tobacco on the suction strip is mechanically brought back to the hopper. However, in some machines, there is no second fan. An example of a typical machine comprising two fans is described in US Patent No. 3,019,793 belonging to

the present holder.

  According to a first aspect of the present invention, it relates to a method for feeding tobacco to a cigarette making machine which consists in transporting tobacco particles in a stream of air from a device delivering the tobacco to a hopper system, measuring the tobacco in the hopper system and pneumatically transporting the tobacco in a stream of air to an air permeable suction strip to form, by extraction of the stream of air, a layer of tobacco to be delivered to the means for forming a tobacco rod of the cigarette making machine, characterized in that atmospheric air is induced in the tobacco delivery device and it is successively used to drive and transport the tobacco particles from the delivery device to the hopper system and to drive and transport the tobacco particles from the hopper system to the suction belt, the tobacco particles being released of the entrainment by the air stream at an inlet of the hopper system and the measured tobacco coming from the hopper system being again entrained in at least part of the same air stream, the hopper system operating at one pressure below atmospheric pressure prevailing in the air stream separated from the

  tobacco particles delivered by the delivery device.

  According to a second aspect of the present invention, the subject of the present invention is a device for delivering tobacco to a cigarette-making machine, characterized in that it comprises: a device for delivering tobacco comprising means for entraining particles of tobacco in an air flow induced in the device; a first transport pipe for receiving the entrained particles, a hopper system for receiving particles from the downstream end of the pipe and comprising means at the inlet of the hopper system for releasing the particles from the current drive transport air; means for measuring tobacco particles received from the hopper system; a second pipe for receiving said particles measured at the outlet of the hopper system, an air-permeable suction band receiving said particles and shaping them into a current which is delivered to the tobacco rod forming means of the machine making cigarettes and means, for extracting air at least through said air permeable strip so that said particles are transported from the hopper system and directed to said strip, said hopper system comprising at least a pipe system provided with an intake orifice receiving air at. a pressure below atmospheric pressure, coming from the means releasing the particles from the drive and an evacuation orifice delivering air to the means for driving the tobacco particles, downstream of said means for measuring the tobacco particles and an enclosure for the hopper system in order to maintain it at said pressure below atmospheric pressure, so that at least part of the same air stream which ceases to entrain tobacco particles at the entry of the system hopper

  is used to drive them again through the second line.

  The present invention eliminates the need to provide a valve or an airlock on each cigarette making machine and it makes it possible to remove at least one of the fans provided in each machine, while providing

  other advantages which will become apparent from reading the description

  made below with reference to the accompanying drawings which illustrate two exemplary embodiments devoid of any limiting nature. In the drawings: FIG. 1 is a schematic view of a preferred embodiment of a device according to the invention, comprising two fans and FIG. 2 is a schematic representation of a variant of the

  device of Figure 1, comprising a single fan.

  Referring to FIG. 1, it can be seen that the device according to the invention comprises a continuously moving, breathable suction band system, designated as a whole by the reference 8, which is associated with a cigarette making machine, (not shown elsewhere), a

  hopper system 10 and tobacco delivery device 12.

  This tobacco delivery device 12 receives cut tobacco in a container 16 which is provided with a control system 14 which monitors and controls the level of tobacco in the container 16 to regulate the supply of tobacco to the container from a source of unopened cut tobacco (not shown). The container 16 constitutes an unopened cut tobacco reservoir 18, making it possible to continuously (or substantially continuously) feed the hopper system 10 with a suitable quantity of tobacco making it possible to meet the requirements of the cigarette making machine . The container 16 communicates at its lower end with an enclosure 20 which contains a pair of counter-rotating measuring drums mounted on pins (or having pins) 22 and a tobacco opening or aeration drum 24 also mounted on spindle, which provides a premeasuring and pre-opening of the unopened cut tobacco at a speed which is substantially equal to the speed at which the tobacco is used for the formation of a cigarette rod by the cigarette manufacturing machine, from the filling material, on the suction strip. This speed is regulated by the control device 26, which is positioned in a measuring tube 28 of the hopper system and which monitors and controls the level of tobacco in the tube 28 so as to deliver a feedback signal, which controls the speed of rotation of the measuring drum 22. If the device 26 comprises a vertical column of photoelectric cells, the speed can be adjusted step by step, according to the number of photoelectric cells in front of which the tobacco passes. According to a variant which may involve a substantially continuous, but not totally continuous, supply, the drums 22 can be at single speed while being able to be stopped.

  when the tobacco column in the tube 28 exceeds a predetermined height.

  Particles of cut tobacco, pre-measured and covered 30, coming from the delivery device 12 are brought into a current of transport air 32, which is induced by the vacuum prevailing in the enclosure 20 by means of a fan 34 which is associated with the cigarette making machine. The air 32 enters the enclosure 20, through an intake orifice 36 so as to entrain the tobacco particles 30 in the air stream 32 and to transport them to the

  across a tobacco line 38 to the hopper system 10.

  The tobacco particles 30 transported by the air, enter the hopper system 10, via a pipe 40, curved downwards, opening into an area situated above the level of the tobacco contained in the tube. measuring 28. The tobacco particles 30 are, in this region of the measuring tube 28, disengaged from the drive. The transport air stream 32 fluidizes an upper layer 44 of tobacco in the measuring tube before being sucked upward through a filter 42 and this fluidization ensures uniform distribution of the tobacco particles 30 over the entire width of the measurement tube 28 (perpendicular to the drawing plane), this width possibly being for example of the order of 600 mm when the diameter of the pipe 38 is typically 100 mm. The filter 42 separates the tobacco particles 30 from the transport air stream 32. The measuring tube 28 receives the transported tobacco and, consequently, it constitutes a tobacco reservoir 46 which communicates by its lower end with an enclosure 50 containing a pair of counter-rotating measuring drums 52 mounted on a spindle and an opening drum 54 mounted on a spindle. The opening drum 54 ensures a distribution in rain of the measured and separated tobacco particles 56 on a conveyor belt 58, according to a flow speed which is equal to the quantity of tobacco necessary for the formation of a cigarette rod. increased by a predetermined excess so as to obtain trimmed tobacco using a pair of deburring discs 62 in the device 8. The flow speed is regulated using a control system 64 located in an equalization column 66. The control device 64 comprises a column of photoelectric cells which control the level of tobacco in the column 66 and which regulate the speed of the measuring drums 52, step by step, in

  function of the number of photoelectric cells in front of which the tobacco passes.

  The conveyor belt 58 transports the separated tobacco particles 56 in front of a magnet 68 which removes all ferrous metals. The density equalization column 66 is filled uniformly and homogeneously with separate tobacco particles 56 and, at its lower end, it delivers a tobacco carpet of uniform density on a transfer drum 72. A beater roller 74 then removes the tobacco particles from the drum 72 and it projects them into a stream of transport air 76 at the required speed. The speed of the drum 72 can be adjusted using a device (not shown) which controls the weight of the finished cigarette rod. The transport air stream 76 is in fact a part of the conveying air stream 32 which drifts the main part of the hopper system through the air line 78 to a rectangular opening 80 which directs the flow of air in a region between the transfer drum 72

and the beater roller 74.

  The separated tobacco particles 56 are transported through a log extraction device 82 which includes a guide 84 which can be adjusted so as to obtain the desired log extraction effect. The logs 86 thus extracted from the tobacco are brought by a screw conveyor 88 into a log collector (not shown). From the extraction system 82, the separated tobacco particles 56 are transported by the air stream 76, upwards, through a chimney 90 to the suction strip 48 which transports a layer of tobacco particles. tobacco accumulated 92 from the top of the chimney 90, through a vacuum seal 94, to the pair of discs

deburring 62.

  In order to facilitate the representation of the entire device in the drawing, the upper part of the chimney 90 has been shown schematically, it being understood that it should be turned at an angle of 90 by

  relative to a vertical axis. The same remark applies to Figure 2.

  The separation of the tobacco particles 56 from the transport air stream 76 is carried out in stages using two filters 96 and 98 which are located respectively at the bottom and at the top of the chimney 90 and also at the bottom. Using the air permeable suction tape 48. A perforated plate 100, located in an air line 102 which communicates with the filter 96, determines the amount of air flow that is deflected into the pipe 102 from the transport air stream 76 so that the remaining air flow can transport the tobacco particles 56 to the suction strip 48 at a predetermined speed. The tobacco layer 92 and the air permeable suction strip 48 act equivalent to a perforated plate and therefore a predetermined amount of the air flow is removed from the chimney in a suction chamber 104. A perforated plate 106, located in an air line 108 which communicates with the filter 98, allows the rest of the transport air stream 76 to pass through the air line 108. The air flow through filters 96 and 98 provides a "compression" effect in that it allows the tobacco to be transported through the chimney at a higher speed than that which would be possible if all the flow d in the

  chimney was sucked through the suction strip 48.

  The suction chamber 104 extends along the device 8 beyond the chimney 90. As described above, the tobacco layer 92 and the air-permeable suction strip 48 act in the same way as perforated plate and therefore an air flow 110, having a predetermined speed, flows from the surrounding atmosphere into the suction chamber 104. This air speed determines the degree of adhesion of the particles tobacco outside the main part of the tobacco layer 92. The magnitude of the pressure drop across the tobacco layer 92 and the breathable suction strip 48, determines the degree of adhesion from the tobacco layer 92 to the suction strip 48. Appropriate control of the transfer of the tobacco layer 92 from the chimney 90 into a lining (not shown) of the cigarette-making machine, depends on the amplitudes of these two parameters and the required value of the vacuum in the suction chamber 104 det ermine the

  suction height of a fan 116 connected to the chamber.

  The air lines 102 and 108 communicate with the fan 34 via the air lines 112 and 114. The suction chamber 104

  communicates with the fan 116 via an air line 118.

  As already mentioned above, the pair of deburring disc 62 deburrs a predetermined excess of tobacco 60 in a collector 120. This collector delivers the deburred tobacco particles 60 in a flow of induced transport air 62 under the effect of the vacuum in the measurement tube 28 of the hopper system 10. The air stream 122 transports the trimmed tobacco particles 60 through a trimmed tobacco pipe 124 which communicates with the tobacco pipe 38 of so as to mix the tobacco particles 30 and 60, these particles entering the vacuum hopper system 10, via the

  line 40 to then be collected in the measurement tube 28.

  The speed at which the tobacco moves through line 38, which connects the delivery device 12 to the hopper system 10, is adjusted using a perforated plate 128 positioned in an air line 126. The perforated plate 128 deflects part of the transport air stream 32 through the air line 126 into the main air line 114 of the fan 34, so that the flow rate of the air stream 32 can be adjusted without affecting the speed of the air stream 76 which enters through the rectangular opening and which then passes into the chimney 90 via the device

82.

  It is possible to interrupt the circulation of the transport air stream 32 when, for one reason or another, tobacco particles 30 coming from the delivery device 12 block the admission to the tobacco pipe 38. The speed of the transport air stream 76 will then be determined by the flow of air through the trimmed tobacco pipe 124, but the resulting reduced speed of the transport air stream 76 will not be sufficient to transport safely and reliably the tobacco particles 56 from the beating roller 74, via the extraction device 82 and from the chimney 90 to the suction strip 48. At the same time, the lower air speeds through perforated plates 100, 106 and 128, considerably increase the value of the vacuum in the chimney 90. Under these conditions, the extraction device 82 and the chimney 90 cease to

  function, which results in additional waterlogging in this area.

  In order to avoid such an obstruction, an additional connection is provided between the atmosphere and the air line 78 using a butterfly valve 38 which is controlled by a vacuum detector 132 located on the air line. 78. The flow

  additional air is controlled by a perforated plate 134.

  If, for one reason or another, tobacco particles clog the upper part of the chimney 90, the transport air stream 32 in the tobacco line 38 and the transport air stream 122 in the supply line trimmed tobacco 124 does not reach the speed required to ensure reliable transport of the tobacco particles 30 or the trimmed tobacco particles 60, there may be an ingestion of additional tobacco either at the entry into the tobacco line 38, or at the entrance to the trimmed tobacco pipe 124, or even at these two locations. To avoid this inconvenience, an additional air connection is provided between the air line 78 and the line 114, using a butterfly valve 136 which is also controlled by a vacuum detector 138 located in the line d air 78. The additional air flow is controlled by a

perforated plate 140.

  It is understood that the value of the vacuum developed in the hopper system 10 will be considerably reduced when no tobacco particle 30 is present in the transport air stream 32 as is generally the case when the machine is started. cigarette making machine. A decrease in the vacuum in the hopper system 10 automatically results in a decrease in the speed of the transport air stream 122 in the trimmed tobacco line 124, which can cause a clogging of the tobacco at the inlet of the tobacco line trimmed 124. In order to avoid this drawback, an additional butterfly valve 142 is provided which has an orifice in its articulated plate and which is located in the inlet orifice 36 towards the enclosure 20 of the delivery device 12. This valve throttle valve 142 is controlled by a vacuum detector 144 which is located in the upper part of the hopper system 10, the desired transport speed of the deburred tobacco particles 60 being then determined

  by the dimensions of the hole in the butterfly valve plate 142.

  Assuming that the value of the vacuum in the enclosure 20 of the tobacco delivery device 12 decreases, the speed of the transport air stream 32 may decrease below an acceptable level. This causes a blockage of tobacco at the entrance to the pipe 38. In order to avoid this drawback, a vacuum detection system 146, positioned in the enclosure 20 stops the drums 22 and 24 so as to interrupt the discharge of the particles tobacco 30 from the tobacco delivery device 12 into the transport air stream 32.

  The device shown in Figure 2 is identical to that described above

  above with reference to FIG. 1, the essential difference being that this variant according to the invention comprises only one fan 148. Thanks to this arrangement, the air ducts 114 and 118 communicate with the fan 148 via the intermediary of an air line 150. In order to obtain the same operation of this device as that of the device described above with reference to FIG. 1, the line 114 is associated with two butterfly valves 152 and 154 and a perforated plate 156. This arrangement makes it possible, if necessary, to release the vacuum in the hopper system 10. The additional air flow is controlled by the perforated plate 156 so that the vacuum in the chamber

  104 is not changed.

  The operation of the device according to FIG. 1 will now be described.

  Under normal production conditions, the butterfly valves 130 and 136 are closed and the valve 142 is open. The vacuum which is created by the fan 34 induces the transport air stream 32 in which the pre-covered and pre-measured tobacco particles 30 are entrained, these particles being extracted from the container 16 of the delivery device 12. The tobacco particles 30 are then transported through the tobacco line 38 in the measurement tube 28 of the hopper system 10. Then, open and measured tobacco particles 56 rain on the conveyor belt 58, they are transported in front of the magnet 68 which removes all ferrous metals and then they are delivered to the density equalization column 66. This column 66 discharges a uniform carpet of tobacco 70 on the transfer drum 72. The beater roller 74 then projects the separated tobacco particles 56 from the tobacco carpet 70 in the transport air stream 76, which is a partial extension of the transport air stream 32. The separated tobacco particles 56 are transported through the rod extraction device 82 then brought by the air stream 76 to the top of the chimney 90 on the suction strip 48 which then transports a layer 92 of tobacco particles accumulated from the top of the chimney 90 to the through a vacuum joint 94 of the chimney, then this layer passes in front of the pair of deburring discs 62 and finally into the rod-forming device (not shown) of the cigarette-making machine. The trimmed tobacco 60 is delivered into the transport air stream 122 and is transported through the trimmed tobacco pipe 124 to be

  brought back into the measuring tube 28 of the hopper system 10.

  When the cigarette making machine, including the moving parts of the hopper system 10, stops for any reason, the control device 26, which is located in the measurement tube 28 of the vacuum hopper device 10, detects an increase in the level of tobacco in the measuring tube and it stops the discharge of the tobacco particles 30 from the delivery device 12 into the transport air stream 32. When an appropriate purge interval has elapsed , (so as to empty the tobacco line 38 of the tobacco particles 30), the fan 34 is stopped and the butterfly valve 142 in the device 12 for delivering tobacco is closed. The system is then ready for restarting the machine for manufacturing

cigarettes.

  Assuming that the tobacco particles 30, discharged from the tobacco delivery device 12, clog up for any reason the entry of the tobacco pipe 38, the vacuum detector 146 in the enclosure 20 of the device

  tobacco delivery 12, interrupts the discharge of the tobacco particles 30.

  At the same time, the vacuum detector 132, positioned in the air line 70, opens the butterfly valve 130 and stops the operation of the cigarette making machine. When the tobacco clogging has been eliminated and the system is ready to operate, a logic unit controls the closing of the butterfly valve 130 and the starting of the system, which begins with a purging interval. When this purge interval has elapsed, the butterfly valve 142 closes and the system is ready for starting the cigarette making machine. In the hypothesis where, for whatever reason, the tobacco particles 56 obstruct the upper part of the chimney 90, the vacuum detector 138 opens the butterfly valve 136 and interrupts the operation of the cigarette making machine. The control device 26, located in the measuring tube 28 of the vacuum hopper 10 interrupts the discharge of the tobacco particles 30 from the tobacco delivery system 12 into the transport air stream 32. When a time of purge has elapsed, fan 34 stops

  and the butterfly valve 142 in the tobacco delivery device 12 closes.

  l When the obstruction due to tobacco is eliminated, the system is ready for a

  restart of the cigarette making machine.

  When an unacceptable high pressure loss occurs in the dust separator, which is located in the cigarette making machine, or in the filter 42, which is located in the upper part of the hopper system 10, the vacuum prevailing in the enclosure 20 of the tobacco delivery device 12 decreases and the same effect can be caused by an unacceptably high leakage of air into the system. The speed of the transport air stream 32 may then not reach the speed necessary for reliable transport of the tobacco particles 30 and, consequently, when the value of the vacuum in the enclosure 20 decreases until it reaches at a critical level, the vacuum detector 146 interrupts the evacuation of the tobacco particles 30 and stops the cigarette making machine. When the purge time has elapsed, the fan 34 stops and the butterfly valve 142 closes. After the vacuum has been restored, the system is ready for a restart of the

manufacture of cigarettes.

  When the supply of cut tobacco from the measurement tube 16 of the tobacco delivery device 12 is interrupted, the command and control device 14, positioned in the measurement tube 16, stops the discharge of the tobacco particles from the device tobacco delivery 12. The

  control device 26 then stops the cigarette making machine.

  When the purge time has elapsed, the butterfly valve 142 closes. When the tobacco supply resumes, the system is ready for a restart of the

  cigarette making machine.

  When starting the cigarette making machine, the command and control device 26, placed in the measuring tube 28 of the vacuum hopper system 10, starts the unloading of the tobacco particles 30 from the delivery device de.tabac 12 in the air stream 32. When the value of the vacuum in its vicinity reaches a required level, the vacuum detector 144 controls the opening of the butterfly valve 142. The system

  then operates under normal production conditions.

  The variant of the invention illustrated in FIG. 2 works in the same way, the fan 34 of the exemplary embodiment shown in FIG. 1 being simply replaced by the pair of butterfly valves 152 and 154

as described above.

  In the exemplary embodiment according to FIG. 1 and also according to FIG. 2, it is also possible to provide additional means making it possible to project a flow of tobacco from the pipe 38 over the width of the measurement tube 28, according to a technique known, for example using fixed deflectors or by means of an insulating deflector. In this regard, it is understood that the width of the measurement tube 28 (which may for example be of the order of 600 mm) corresponds to

that of the chimney 90.

  According to the invention, the conveyor 58 can be replaced by a drum.

  It remains to be understood that the present invention is not limited to the embodiments described and shown but that it encompasses all variants thereof.

Claims (20)

  1- A method for feeding tobacco to a cigarette making machine which consists of transporting tobacco particles in an air stream from a tobacco delivery device to a hopper system, to measure the tobacco in the hopper system and pneumatically transporting the tobacco in an air stream to an air permeable suction band, in order to form, by extraction of the air stream, a layer of tobacco to be delivered to the means for forming a tobacco rod from the cigarette making machine, characterized in that atmospheric air is induced in the tobacco delivery device and it is used successively to entrain and transport the tobacco particles from the device for delivery to the hopper system and for entraining and transporting the tobacco particles from the hopper system to the suction belt, the tobacco particles being released from the entrainment by the air stream to an inlet of the hopper system e hopper and measured tobacco from the hopper system being again entrained in at least part of the same air stream, the hopper system operating at a pressure below atmospheric pressure prevailing in the air stream   separated from the tobacco particles delivered by the delivery device.   2- A method according to claim 1, characterized in that the air ensuring the re-entrainment of the measured tobacco particles coming from the hopper, is extracted partially through the suction strip and partially through at least one filter in a pipe, in which particles of   tobacco are transported to the suction band.   3- Method according to one of claims 1 or 2, characterized in that   the vacuum level is detected at one or more points of the system in order to produce one or more signals to control valves which operate automatically to improve poor operating conditions due to   possible obstruction of a pipe by tobacco.   4- Method according to any one of claims 1 to 3, characterized   in that the tobacco is transported substantially continuously from the delivery device to the hopper system at a speed, or an average speed, controlled by the level of tobacco accumulated in the hopper system, in order to   maintain the level of accumulated tobacco at a substantially constant value.   - Method according to any one of claims 1 to 4, characterized   in that the particles coming from the delivery device constitute a fluidized bed & the inlet of the hopper system, fluidized bed & from which the   particles are released from entrainment.   6- Process for treating cut tobacco in order to form a stream of tobacco particles on a suction band, permeable to air, in continuous movement, bringing the stream of tobacco to means for forming a rod of tobacco from a cigarette making machine, characterized in that it consists of: - delivering unventilated cut tobacco, in a tobacco delivery device, located at a location remote from the cigarette making machine, so obtaining a source of pre-aerated and pre-measured tobacco particles suitable for air transport; - entraining said tobacco particles from the tobacco delivery device in an induced air flow in the delivery device using a fan system located in or near the cigarette making machine; - transporting said air stream and the tobacco particles it entrains from said delivery device, through a tobacco pipe to a hopper system which is closed so as to maintain a pressure below the atmospheric pressure; - to measure said particles from the bottom of said container and to transport said tobacco particles in a density equalization column of the hopper system; - to transfer the tobacco particles whose density has been equalized, by a transfer drum from the density equalization column, to a beater roller forming part of the hopper system; - releasing the tobacco particles from the transfer drum by said beater roller; - re-entraining said tobacco particles in at least part of said stream of air released from tobacco particles entering the hopper and directed by a pipe in the region of said beater roller; - To transport said tobacco particles by said air stream, outside the hopper system and through a chimney to said suction strip and - to entrain tobacco particles from said air stream in au. minus a pipe connected to the ventilation means to allow training   of said bed of tobacco particles on said suction strip.   7- A method according to claim 6, characterized in that said air stream is induced by two fans located near or in the cigarette manufacturing machine, one of the fans inducing a portion of said air stream through the air permeable suction strip and the other fan inducing the rest of the air flow through at least one filter in said chimney.   8- Method according to one of claims 6 or 7, characterized in that   the retrained particles leaving the hopper system pass through a   log removal device.   9- Method according to any one of claims 6 to 8, characterized   in that the excess tobacco particles are deburred using deburring discs, from the tobacco stream on the air-permeable suction strip to be brought back to the hopper, in that said particles of excess tobacco are entrained in an air current induced by the pressure below atmospheric pressure, in the hopper of the hopper system and in that the entrained particles are transported by the induced air current towards the tank.   - Device for delivering tobacco to a cigarette making machine, characterized in that it comprises: a tobacco delivery device (12) comprising means (36) for entraining tobacco particles in an induced air stream in the device; a first transport pipe (38) for receiving the entrained particles, a hopper system (10) for receiving particles coming from the downstream end of the pipe and comprising means (40, 42) at the inlet of the hopper to free particles from the entrainment of the transport air stream; means (52) for measuring tobacco particles received from the hopper system; a second pipe (90) for receiving said particles measured at the outlet of the hopper system, an air permeable suction strip (48) receiving said particles and shaping them into a current which is delivered to the rod-forming means tobacco from the cigarette making machine and means (116, 118, 148) for extracting air at least through said air permeable strip so that said particles are transported from the hopper system and directed towards said strip, said hopper system further comprising a duct system (78) provided with an intake orifice receiving air at a pressure below atmospheric pressure from the means releasing the particles from the drive and a discharge orifice (80) supplying air to the means for driving the tobacco particles, downstream of said means for measuring the tobacco particles and an enclosure (50) for the hopper system in order to maintain it at said pr ession lower than atmospheric pressure so that at least part of the same air flow which ceases to carry the tobacco particles at the entry of the   hopper is used to drive them again through said line.   11- Device according to claim 10, characterized in that it comprises means (34, 114, 148, 112) for extracting air from the second   line (90) through at least one filter (96, 98).   12- Device according to claim 11, characterized in that said means for extracting air through at least one filter (96; 98) comprises a fan (34) which is distinct from a fan (116) serving at   extracting air through said air permeable strip (48).   13- Device according to claim 11, characterized in that a common fan (148) is provided for extracting air through the strip   (48) and at least one filter (96; 98).   14- Device according to any one of claims 10 to 13,   characterized in that it comprises one or more additional air flow pipes (126; 140; 134) designed so as to improve the poor operating conditions possibly caused by an obstruction of a driven by tobacco.   15- Device according to claim 14, characterized in that it comprises one or more valves (130; 136; 142) controlled by vacuum detectors (132; 138; 146) to improve the poor conditions of   functioning due to a possible obstruction of a pipe by tobacco.   16- Device according to any one of claims 10 to 15,   characterized in that the tobacco delivery device (12) is designed so as to transport tobacco, substantially continuously, to the hopper system (10), at a speed or an average speed, controlled by the level of the tobacco ( 46) accumulated in the hopper system to maintain this level at a substantially constant value.   17- Device according to claim 16, characterized in that the tobacco delivery device (12) comprises a container (16) for receiving and storing cut tobacco, two counter-rotating measuring drums (22), below the container for the advancement of cut tobacco at a feed rate substantially equal to the requirements of the cigarette making machine, an aeration drum (24) for opening the tobacco fibers, below the measuring drums, for separating said cut tobacco into particles which can be entrained by air and for discharging said particles into a entrainment zone leading to said tobacco pipe (38) towards the hopper system and means delimiting an air intake orifice (36) in said drive zone through which an air current (32) is induced to   entrainment of said tobacco particles.   18- Device according to claim 17, characterized in that the hopper system (10) comprises: a tobacco tank delimited inside said enclosure and which comprises an upper inlet in which comes the tobacco transport pipe ( 38) from the delivery device (12) and which forms a fluidization chamber in which the tobacco particles separate from the transport air stream; two counter-rotating measuring drums (52), below the tank, for advancing the tobacco particles according to the required feeding speed; an aeration drum (54) below the measuring drums for separating the tobacco particles, said aeration drum discharging the separated tobacco particles on a conveyor (58); a density equalization line (66) receiving tobacco particles delivered by said conveyor (58); a transfer drum (72) for transferring equalized density tobacco particles from said density equalization line to a threshing roller (74) for engaging said tobacco particles from the transfer drum and a bypass line (78) receiving at least part of the air stream separated from the tobacco particles in the inlet part and discharging them into an opening (80), in the region of the beating roller, so as to entrain the particles of   released tobacco and to transport them in and through the second pipe (90).   19- Device according to claim 18, characterized in that the upper part of the reservoir (28) contains a downwardly curved pipe (40) constituting the downstream end of the tobacco pipe (38) of the delivery device, this pipe curved downwards being oriented so as to direct said air stream towards the upper surface of the tobacco particles accumulated in the tank, so that the air stream penetrates and fluidizes the highest part of said tobacco particles and a filter (42) above the end of the pipe to intercept parasitic tobacco particles   the inlet of the bypass line.   - Device according to one of claims 18 or 19, characterized in that   that it comprises means for extracting tobacco logs (82), located at the outlet of the hopper system to separate the logs from entrained tobacco particles and in that a vertically extending chimney forms the second pipe for pneumatic conveying of tobacco particles, upwards, to the continuously moving air permeable suction band (48), which   closes the upper end of said chimney.   21- Device according to any one of claims 18 to 20,   characterized in that said log extraction means comprise a curved channel whose curvature adapts to that of the beating roller, an adjustable guide (84) for deflecting heavy particles constituting logs, separated from tobacco particles and means (88) to collect and remove said   heavy particles constituting the logs.   22- Device according to one of claims 20 or 21, characterized in that   that said chimney (90) has a lower filter (96) for extracting part of said air stream, so that said tobacco particles are transported upward through said chimney to the air permeable suction strip at a predetermined transport speed and an upper filter (98) for extracting the excess air remaining from the air extracted through the tobacco filling and the air permeable strip (90), in a   vacuum chamber (104) above said strip.   23- Device according to any one of claims 10 to 22,   characterized in that it comprises a pair of deburring discs (62) positioned so as to deburr the excess tobacco from the tobacco transported by said breathable strip (48), a collector (120) placed so as to collect the deburred tobacco particles removed by said pair of deburring discs and a line (124) which connects said manifold to the inlet region of the hopper system so that the pressure below atmospheric pressure in said hopper system induces a flow air in said line which   entrains the deburred tobacco particles and brings them back to the hopper system.